#include<stdio.h>
int check(double mid,int k,int b,int c)
{
	double a=k;	
	for(int i=1;i<=c;i++){
		a=a+a*mid-b;
	}
	if(a > 0) return 1;
return 0;
}
int main()
{
	int a,b,c;
	double ss;
	scanf("%d %d %d",&a,&b,&c);
	double l=0,r=500,mid;
	while(r-l>1e-5)
	{
		mid=(l+r)/2;
		if(check(mid,a,b,c)) r=mid;
		else l=mid;
	}
	printf("%.1f",l*100);
	return 0;
}